This is a daemon that listens to xilinx_xvc (xilinx virtual cable) traffic and operates JTAG over an FTDI in either bitbang mode or in MPSSE mode.

The bitbang mode is the original code with slight modifications with changes to the arguments of the interface functions. After building, the executeable that uses bitbang mode is called xvcdbb. From the original README: "This version is hardcoded to use an FTDI cable with an FT2232C chip. It does not use MPSSE but rather bitbang mode. It uses ftdi_write_async which might not be available on your platform. You can use the (much slower) non-async version instead."

For MPSSE mode, which can be faster than bitbang mode, the output executable is called xvcdmp. As a comparison, for a Xilinx Zync XCXC7Z020 and using Vivado 2017.4, programming the Zynq FPGA logic directly can take about 35 seconds through bitbang_mode and about 27 seconds with MPSSE mode. Have tested this with both a FT2232H and a FT4232H. Both MPSSE ports of either of these devices can be used by selecting it through the -i option.

Additionally, if desire to use this with a BCP board, which has a built-in FT4232H, use the executable called xvcdbcp. This uses MPSSE mode but sets up the FTDI I/O in a way specific for use on the BCP. Still use xvcdmp if using this with a generic FTDI cable or development board.

If you do not desire to use this with a BCP board, it may be best to revert to v1.0. Only the new xvcdbcp executable has been tested. xvcdbb and xvcdmp are expected to function as before but the code changes made to get the BCP specific code inserted could have an unintended consequence. There was just not time to fully test those older executables.

If having trouble connecting to the JTAG target, try forcing the frequency lower with the -f option. However, this is only used by the MPSSE mode version.

If use the -i option to select a different interface on a multiple interface device like the FT2232H and FT4232H, keep in mind that for MPSSE mode, only interface 0 & 1 have MPSSE engines and you will get an error if try to select interface 2 or 3. However, for bitbang mode, can use all 4 interfaces.

One key to speeding up both the bitbang and MPSSE modes is setting the USB latency timer setting to a lower value in io_init(). However, this may have a detrimental impact on the host system. If the host is a Raspberry Pi, which this was tested on, it seems fine. If the host is a PC with lots of USB devices, you may need to increase the latency timer value. This can be done with the LATENCY_TIMER make variable (ie. make LATENCY_TIMER=16)

Also, the base server code was merged with https://github.com/Xilinx/XilinxVirtualCable/blob/master/XAPP1251/src/xvcServer.c so that Xilinx Virtual Cable is fully supported through both ISE and Vivado.

To try to determine the IP address where the executable is running in order to tell the user, the ethernet interface must be selected by defining USE_GETIFADDRS to the interface name. This can be done through a make variable (ie. make USE_GETIFADDRS=wlan0). If do not define it, then the code is skipped.

Need both libusb and libftdi1 libraries. See individual README_xxx.txt files with extensive comments on how to install/build libusb and libftdi for this build.

The BCP board has both a FTDI FT4232H interface and a JTAG header. So when the XVC server is asked to connect over JTAG, the server first checks that a programmer is not already plugged in. If one is plugged in, the server refuses to change the JTAG I/O settings so as to not conflict with the external JTAG programmer. This will result in the user receiving an error when trying to open the XVC server connection. If you really intended to use the XVC connection, you must first remove any external JTAG programmers from the JTAG header.

Conversely, if you want to use an external JTAG programmer, you must have the executeble xvcdbcp running. By default, the FT4232H grabs the JTAG I/O, unfortunately. By running xvcdbcp, the FT4232 is told to release the JTAG I/O at start-up. This allows an external programmer to be used. The other option is to simply unplug the USB cable from the FT4232 port. However, this port also handles the IPMC and ELM serial consoles, which will get closed down if the USB cable is removed.

So, if you want the IPMC or ELM consoles, the best practice is to always have xvcdbcp running and then the user can chose whether to use an external programmer or the XVC server from the Hardware Manager.

If switching between external programmer and XVC server, Close Server in Hardware Manager first. This will disconnect from the XVC server which triggers the server to switch I/O back into IDLE mode where the JTAG signals are released. Close Target does not disconnect from the XVC server and so control of the JTAG pins does not change in that case.

Have fun!